This invention relates to a mechanism for feeding a stick type cosmetic material (lipstick, eye liner, etc.), etc. and to a container employing the same. More specifically, this invention relates to a mechanism for feeding a stick type cosmetic material utilizing a push rod having a group of protrusions which function as an external thread and, as necessary, rotation-stop ribs, which has a simple structure and can be produced easily, as well as, to a container for feeding a stick type cosmetic material, etc., utilizing such mechanism.
Examples of prior art mechanism and container for feeding a stick type cosmetic material will now be described. Containers for feeding stick type cosmetic materials include those of cartridge type and non-cartridge type. In the cartridge type container, cartridges respectively containing different colors of core materials (hereinafter referred to as stick type cosmetic materials) are provided, and a user selects and replace the desired cartridge and sets it in the body of the container.
FIG. 12 shows in cross-section the structure of the body of a prior art cartridge type container disclosed in Japanese Utility Model Publication No. 50814/1991. In a main body 200 are housed a push rod 201 and an inner barrel 207. The push rod 201 is provided on the circumference at the rear end portion thereof with an external thread 205, while the rest of the portion on the circumference of the push rod 201 is provided with elongated ridges 206. Meanwhile, the inner circumference of the inner barrel 207 is provided over the entire length thereof with an internal thread 209 which is engaged with the external thread 205. The inner barrel 207 is also provided with elongated ridges 213 on the outer surface thereof, which engage with grooves 211 formed on the inner surface of an outer barrel 215.
After a cartridge is inserted through the tip opening 217 of the outer barrel 215 of the main body 200 and the rotation-stop section of the cartridge and the elongated ridges 206 of the push rod 201 are engaged, the cartridge and the main body 200 are turned relative to each other (e.g. one is immobilized, and the other is turned), whereby the push rod 201 can be advanced or retracted in the axial direction. On the other hand, in a non-cartridge type container, the stick type cosmetic material is inserted to a chuck provided at the tip of the push rod 201, and the push rod 201 (external thread 205) and the inner barrel 207 (internal thread 209) are turned relative to each other using some means, for example, a cylinder disposed around the stick type cosmetic material which is designed to be engaged with the elongated ridges 206 of the push rod 201. In any case, the push rod 201 is designed to be advanced or retracted in the axial direction of the main body to allow the stick type cosmetic material to be fed out or retracted.
In the prior art feeding mechanisms, the external thread and the rotation-stop section (ribs etc.) formed on the push rod, and the internal thread formed in the main body are essential elements. Accordingly, a complicated design or working has been required so as to form these elements into respective parts. For example, the feeding mechanism disclosed in Japanese Utility Model Publication No. 50814/1991 (FIG. 12) involves the following problems.
(1) Since the internal thread 209 of the inner barrel 207 is long, molding and working take much time and labor; PA1 (2) The diameter of the internal thread 209 cannot be reduced due to the limitation in molding and working thereof (e.g. strength of injection molding core pin and working thereof), so that the diameter of the container itself cannot be reduced; PA1 (3) If the push rod 201 is provided on the outer circumference substantially over the entire length thereof with the external thread, the length of the internal thread to be engaged therewith can be short. However, elongated ridges or grooves as a rotation-stop mechanism must be provided on the surface of the external thread of the push rod, inevitably making the shape of the push rod complicated, as shown in FIG. 13. In FIG. 13, a push rod 305 is provided on the circumference with an external thread substantially over the entire length thereof, and ribs 321 are provided at the crest of the external thread 323. The external thread 323 is engaged with the internal thread 311 of the main body 301, while the ribs 321 are engaged with the engagement grooves 351 formed in the cartridge 341, whereby the cartridge and the push rod can be turned synchronously. Contrary to the constitution shown in FIG. 13, grooves may be formed on the crest of the external thread of the push rod, and ribs may be formed in the cartridge; and PA1 (4) If a push rod having an external thread formed on the outer circumference thereof is to be formed by injection molding using a split mold, there are strict limitations on the diameter and the pitch of the thread so as to prevent undercut which is liable to occur in mold releasing, and thus the resulting thread inevitably comes to have a short pitch, giving rise to a problem in the operability of the feeding mechanism.